Recently while setting up an IFD demo environment we faced below issue while we tried to access ADFS metadata endpoint using ADFS server name. But when we tried to access it using server IP address it was working fine (We already did changes in host file)

To resolve this issue we disabled “IE Enhanced Security Configuration (ESC) (you can access this from Server Manager -> Security Information)

After that we were able to browse ADFS metadata service using ADFS server name.

Reference : https://social.technet.microsoft.com/wiki/contents/articles/1429.ad-fs-2-0-browsing-to-federation-metadata-fails-unable-to-download-federationmetadata-xml.aspx